Effects of reflective surfaces on silicon emissivity and temperature measurements

The effects of front-side reflective surfaces on the sensitivity and temperature measurement of silicon wafers in a Rapid Thermal Processing chamber with backside heating are examined through optics modeling. Two schemes are contrasted. In (1), the pyrometry detector looks at the backside of the wafer; in (2), it looks at the frontside of the wafer. In both cases, the temperature errors occur when the reflector's reflectivity deviates from unity. However, the error dependence on the reflector reflectivity exhibits interesting differences in these two schemes. Under the working conditions proposed in this paper, a non-ideal reflector introduces a bigger temperature error in the 'backside-detector' scheme than in the 'front-detector' scheme. Practical implications of these results are also discussed.